Embodiments of the present disclosure generally relate to a power-supply voltage sensing device, and more particularly to a technology for sensing a level of an external power-supply voltage during a test mode.
Voltage stability of a semiconductor integrated circuit (IC) is of importance to operational stability and reliability of the semiconductor IC.
A reference voltage generation circuit which generates a reference voltage with a predetermined voltage level may be helpful in maintaining internal voltages of the semiconductor IC at desired voltage levels even in a situation where an external power-supply voltage changes.
However, the reference voltage generated from the reference voltage generation circuit may vary depending not only on a change in the external power-supply voltage, but also on a deviation in a fabrication process and a temperature change of the semiconductor ICs.
In order to find various defects generated during the fabrication process of the semiconductor ICs, various tests are carried out on wafers and packages of the semiconductor ICs. Typically, in order to find the defects that may occur in an actual condition and environment, the above tests are performed under harsher conditions and environments than the actual conditions and environments.
Examples of the harsh test conditions may include various parameters such as temperature, voltage, test pattern, and test time. Here, an operation for increasing an internal power-supply voltage may be carried out by changing an operation voltage of an internal circuit.
With the development of new technologies, a reference voltage generation circuit of the semiconductor IC adjusts the external power-supply voltage, and an internal voltage driving unit of the semiconductor IC converts from the external power-supply voltage to the internal power-supply voltage of the internal circuit.
Most semiconductor devices including DRAM use not only an external voltage (e.g., VDD, VSS, etc.) received from an external device, but also an internal voltage, which is generated in the semiconductor devices and different in level from the external voltage.
Typically, the internal voltage is generated using the charge pumping scheme or the voltage down-converting scheme based on a reference voltage corresponding to a target level, an external power-supply voltage (e.g., VDD), and an external ground voltage (e.g., VSS).
Therefore, it is important for the semiconductor devices driven by various operation voltages to be tested by various external input voltages to detect a boundary point of a desired target voltage. This test may be performed by sweeping the various external voltages in various voltage levels.
However, the voltage sweep test takes a long time and is not cost-efficient.